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read_key,lineeedit: parse position answerback faster; sanitize its use

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it's still not reliable, and probably cannot be made so...
added comment with explanation.

function                                             old     new   delta
put_prompt                                            52     110     +58
read_key                                             601     607      +6
lineedit_read_key                                    201     207      +6
win_changed                                          108     104      -4
read_line_input                                     4824    4809     -15
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 3/2 up/down: 70/-19)             Total: 51 bytes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
This commit is contained in:
Denys Vlasenko
2009-10-26 15:23:32 +01:00
parent d31a8793eb
commit 727e1b536e
2 changed files with 58 additions and 33 deletions
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38
libbb/lineedit.c
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@@ -370,6 +370,7 @@ static void input_backward(unsigned num)
static void put_prompt(void)
{
out1str(cmdedit_prompt);
fflush(NULL);
if (ENABLE_FEATURE_EDITING_ASK_TERMINAL) {
/* Ask terminal where is the cursor now.
* lineedit_read_key handles response and corrects
@@ -380,7 +381,33 @@ static void put_prompt(void)
* Note: we print it _after_ prompt, because
* prompt may contain CR. Example: PS1='\[\r\n\]\w '
*/
out1str("\033" "[6n");
/* Problem: if there is buffered input on stdin,
* the response will be delivered later,
* possibly to an unsuspecting application.
* Testcase: "sleep 1; busybox ash" + press and hold [Enter].
* Result:
* ~/srcdevel/bbox/fix/busybox.t4 #
* ~/srcdevel/bbox/fix/busybox.t4 #
* ^[[59;34~/srcdevel/bbox/fix/busybox.t4 # <-- garbage
* ~/srcdevel/bbox/fix/busybox.t4 #
*
* Checking for input with poll only makes the race narrower,
* I still can trigger it. Strace:
*
* write(1, "~/srcdevel/bbox/fix/busybox.t4 # ", 33) = 33
* poll([{fd=0, events=POLLIN}], 1, 0) = 0 (Timeout) <-- no input exists
* write(1, "\33[6n", 4) = 4 <-- send the ESC sequence, quick!
* poll([{fd=0, events=POLLIN}], 1, 4294967295) = 1 ([{fd=0, revents=POLLIN}])
* read(0, "\n", 1) = 1 <-- oh crap, user's input got in first
*/
struct pollfd pfd;
pfd.fd = STDIN_FILENO;
pfd.events = POLLIN;
if (safe_poll(&pfd, 1, 0) == 0) {
out1str("\033" "[6n");
fflush(NULL); /* make terminal see it ASAP! */
}
}
cursor = 0;
{
@@ -1603,7 +1630,7 @@ static void cmdedit_setwidth(unsigned w, int redraw_flg)
int new_y = (cursor + cmdedit_prmt_len) / w;
/* redraw */
redraw((new_y >= cmdedit_y ? new_y : cmdedit_y), command_len - cursor);
fflush(stdout);
fflush(NULL);
}
}
@@ -1640,6 +1667,7 @@ static int lineedit_read_key(char *read_key_buffer)
ic = read_key(STDIN_FILENO, read_key_buffer);
if (ENABLE_FEATURE_EDITING_ASK_TERMINAL
&& cursor == 0 /* otherwise it may be bogus */
&& (int32_t)ic == KEYCODE_CURSOR_POS
) {
int col = ((ic >> 32) & 0x7fff) - 1;
@@ -1708,7 +1736,7 @@ int FAST_FUNC read_line_input(const char *prompt, char *command, int maxsize, li
) {
/* Happens when e.g. stty -echo was run before */
parse_and_put_prompt(prompt);
fflush(stdout);
/* fflush(stdout); - done by parse_and_put_prompt */
if (fgets(command, maxsize, stdin) == NULL)
len = -1; /* EOF or error */
else
@@ -2190,7 +2218,7 @@ int FAST_FUNC read_line_input(const char *prompt, char *command, int maxsize, li
tcsetattr_stdin_TCSANOW(&initial_settings);
/* restore SIGWINCH handler */
signal(SIGWINCH, previous_SIGWINCH_handler);
fflush(stdout);
fflush(NULL);
len = command_len;
DEINIT_S();
@@ -2204,7 +2232,7 @@ int FAST_FUNC read_line_input(const char *prompt, char *command, int maxsize, li
int FAST_FUNC read_line_input(const char* prompt, char* command, int maxsize)
{
fputs(prompt, stdout);
fflush(stdout);
fflush(NULL);
fgets(command, maxsize, stdin);
return strlen(command);
}